<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script>
      //int num;
      //js是弱类型语言，赋给他什么值就是什么类型
      var v;
      console.log(v);//undefined
      console.log(typeof(v));//undefined
      v = 3.14;
      console.log(v);//3.14
      console.log(typeof(v));//number
      v = 'hello js';
      console.log(v);//hello js
      console.log(typeof(v));//string
      v = true;
      console.log(v);//true
      console.log(typeof(v));//boolean
      v = null;
      console.log(v);//null
      console.log(typeof(v));//object

      var m = '3';
      var n = 3;
      if (m == n) {
          console.log('m==n')
      }
      if (m === n) {
          console.log('m===n')
      }
    </script>
</head>
<body>

</body>
</html>